In conventional pressure reducing valves having control slides actuated by plungers of proportional electromagnets, the force exerted by the plunger of the proportional electromagnet on the control slide opposes the force exerted by the control pressure on the control slide. In order to overcome the force exerted by the control pressure, the proportional electromagnet used must be capable of exerting a greater counterforce. Additionally, the control slide must have its slider piston precisely underlap the control bore controlling the connection to the supply tank, since the flow of the control fluid is determined by such underlap.
In a conventional pressure reducing valve with pilot control, a restrictor is provided in the bore extending longitudinally within the control slide and a pilot valve is connected at the outlet side of this restrictor. The side of the pilot valve facing away from the control slide is connected with the supply tank or a remote control connection. The pilot valve causes a pressure build up which acts in the same direction on the control slide as the force of the spring biasing the control slide. This pressure build up by the pilot valve would not assist a force applied to the control slide which opposes the spring action on the control slide. (see e.g., Dieter, "Oelhydraulik Fibel", KraussKopf Verlag, Wiesbaden, 1960, p. 183).